Keyframes in H.264 videos encoded with mencoder

using the X264 library are not inserted automatically. Why is this important? Well, it is not per-se, but for example if you want to start playback of a video file that is only partially copied/downloaded, the file needs to be interleaved with keyframes (at a specific interval). Apple’s recommendations for Quicktime compatible MP4 videos for example is a keyframe at least every 200 to 300 frames. So make sure to add the following to your mencoder command line:

mencoder -x264encopts ...:keyint=200:...

The same is true for ffmpeg or the x264 binary. This one was buggin’ me for quite some time now and it seems such a simple detail to obvious to miss… 05/25/2012